Rubber composition and a fuel transporting hose for a vehicle

ABSTRACT

A plasticizer having a specific SP value and a specific molecular weight is added to NBR having a specific AN content in an ultrahigh range, or a blend of such NBR and less than 25 percent by weight of PVC so that a good balance may be obtained between its amount and the AN content of the NBR. A fuel hose for a vehicle having an inner wall layer formed from such a rubber composition and an outer wall layer formed from a rubber material having ozone resistance or cure flatting resistance is provided. The rubber composition is of good fuel impermeability and low temperature properties and also has a high conductivity. The hose is of good fuel impermeability and low temperature properties and also has a high conductivity.

TECHNICAL FIELD

This invention relates to a rubber composition and a fuel transportinghose for a vehicle. More particularly, this invention relates to a fueltransporting hose for a vehicle which is simple and inexpensive inconstruction and is satisfactory for fuel impermeability and a certainlevel of conductivity as required of a fuel transporting hose for avehicle, and to a rubber composition used therefor.

BACKGROUND ART

Regulations concerning the permeation of fuel in a vehicle, which aresimilar to the so-called SHED regulation in the United States, are putinto effect in A.D. 2000 in Japan and Europe. As is well known, a fueltransporting hose is highly responsible for the permeation of fuel in avehicle, and measures have been sought for controlling the permeation offuel from a fuel transporting hose.

It has been a common practice in Japan to use FKM (fluororubber) of highfuel impermeability and sour resistance to form an inner wall layer of afuel hose used in what is called a liquid line, such as a feed or returncircuit in a vehicle fuel line. Generally used NBR(acrylonitrile-butadiene rubber), or NBR-PVC which is a blend of NBR andPVC (polyvinyl chloride), has been used for a filler neck hoseconnecting a filler hole and a gasoline tank, or a breather orevaporation hose forming a vapor line. In the United States having theSHED regulation already in effect, the specifications for a filler neckhose or an evaporation hose employ FKM or a resinous material such as apolyamide resin or fluororesin for its inner wall layer and NBR-PVC, ECO(epichlorohydrin rubber), CSM (chlorosulfonated polyethylene rubber) orthe like for its outer wall layer.

The specifications adopted in Japan for the filler neck, breather andevaporation hoses as mentioned above, however, fail to attain any fuelimpermeability conforming to the national regulation going to be putinto effect as stated above. The filler neck or evaporation hose havingan inner wall layer formed from FKM or a resinous material as in theUnited States can be expected to satisfy the regulation in fuelimpermeability. FKM or a fluororesin is, however, expensive, and is solow in reactivity that its bonding to an outer layer material requiresan additional level of technical skill and an additional amount ofprocessing cost. Another drawback is that a complicated manufacturingprocess is required for shaping a hose having a layer of FKM likebellows.

It has also been pointed out that a filler neck or breather hose may becharged with static electricity as a result of e.g. the flow of gasolineduring fill-up or body vibration and may produce a spark when contactedby a metallic fill-up gun, resulting in the ignition of gasoline. It is,thus, hoped that conductivity will be imparted to any such hose (forexample, to the extent giving it a volume specific resistance notexceeding 10⁸Ω·cm) to prevent any electrical charging thereof. It is,however, difficult to impart any satisfactory conductivity, since FKM ora resinous material essentially has a high electric resistance.

Under these circumstances, it is an object of this invention to make afuel transporting hose for a vehicle having high fuel impermeability andconductivity by using a simple and inexpensive rubber composition. Theinventor of this invention has evaluated various rubber compositionscontaining NBR or NBR-PVC as a base material, and has conceived acompound design for a rubber composition which is comparable to FKM infuel impermeability and exhibits high conductivity, while ensuring thenecessary properties including low temperature properties.

DISCLOSURE OF THE INVENTION

It has been pointed out that NBR or NBR-PVC having a relatively high ANcontent of, say, 36 to 42 percent by weight has an improved fuelswelling resistance. However, the inventor's experiment conducted byusing PHASE 11 gasoline for evaluation (gasoline for a permeation testas specified by the U.S. CARB, i.e. SHED test) indicates that NBR orNBR-PVC having such an content is apparently unsatisfactory in fuelimpermeability.

During the process of research work, on the other hand, the inventor hasfound that NBR or NBR-PVC having a specific AN content in an ultrahighnitrite range (for example, 43 percent by weight or higher) has a highfuel impermeability comparable to that of FKM. The inventor has alsofound that, while it is feared that NBR or NBR-PVC having an content inan ultrahigh nitrite range may be undesirably poor in low temperatureproperties as required of a fuel hose for a vehicle (the flexibility ofa hose used in a very cold place having a temperature of as low as, say,−30° C.), the addition of a properly selected plasticizer in a properlyselected amount makes it possible to realize a satisfactory level of lowtemperature properties while ensuring a high fuel impermeability, andthat the proper addition of carbon black (CB) makes it possible torealize satisfactory conductivity while ensuring the propertiesmentioned above.

Moreover, the inventor has found very interesting matters, as shown at(1) to (4) below, about the technical meaning of PVC as a materialblended for such a rubber composition.

(1) PVC is basically a component contributing to fuel impermeability,and it is necessary or beneficial to blend PVC with NBR to impartweatherability and ozone resistance to a rubber composition used formaking an outer layer for a fuel hose having a multilayer wallstructure, or a fuel hose having a single-layer wall. A rubbercomposition containing 25 percent by weight or more of PVC relative toNBR is practically satisfactory in weatherability and ozone resistance.

(2) It is, therefore, not necessary to blend 25 percent by weight ormore of PVC with NBR to make any rubber composition not used for thepurpose as stated at (1) above. On the other hand, it is feared that PVCas a resinous component may lower the low temperature properties of thecomposition. While it is effective in this connection to increase theproportion of the plasticizer, the excessive increase of the plasticizerin the rubber composition results in a reduction of its fuelimpermeability. Thus, an increase in the blend ratio of PVC brings abouta narrowing in the range of proportions which can be selected forachieving a good balance between the fuel impermeability of the rubbercomposition and its low temperature properties.

(3) If the amount of PVC blended is less than 25 percent by weightrelative to NBR, it is possible to secure a broad range of proportionswhich can be selected for making a rubber composition having a goodbalance between fuel impermeability and low temperature properties,while maintaining the contribution of PVC to fuel impermeability asstated above. The amount of PVC is preferably not more than 5 percent byweight if the balance between the fuel impermeability of the rubbercomposition and its low temperature properties is more important thanthe contribution of PVC to its fuel impermeability.

(4) If NBR has an content set in a really ultrahigh range not lower than46 percent by weight, the contribution of PVC to fuel impermeability asstated above can hardly be obtained. In such a case, therefore, it ispreferable in view of the foregoing (1) to (3) to use NBR as a basematerial without blending any PVC.

According to a first aspect of this invention, there is, thus, provideda rubber composition for a fuel transporting hose for a vehicle whichcomprises NBR having an AN (combined acrylonitrile) content of 46 to 52percent by weight as a base material, and 15 to 30 parts by weight of aplasticizer having an SP value (solubility parameter) of 8.8 or more anda molecular weight of 550 or less, relative to 100 parts by weight ofthe base material.

According to the first aspect of this invention in which NBR having anAN content of 46 to 52 percent by weight is used as a base material, NBRhaving such an ultrahigh AN content makes it possible to obtain a highfuel impermeability comparable to that of FKM. The composition contains15 to 30 parts by weight of a plasticizer having the SP value andmolecular weight stated above relative to 100 parts by weight of thebase material. The plasticizer having a molecular weight of 550 or lessis low in viscosity at a low temperature and markedly improves the lowtemperature properties of the rubber composition. The plasticizer havingan SP value of 8.8 or more is well miscible with NBR or NBR-PVC havingthe AN content stated above and does not substantially affect the fuelimpermeability of the rubber composition. Therefore, the rubbercomposition exhibits both a high level of fuel impermeability and asatisfactory level of low temperature properties. Moreover, the properaddition of carbon black (CB) makes it possible to realize asatisfactory level of conductivity, while ensuring the variousproperties as stated above. If the plasticizer has an SP value of lessthan 8.8, its deficiency in solubility with the base material causes itsbleeding and it may fail to contribute effectively to improving the lowtemperature properties of the rubber composition. If the plasticizer hasa molecular weight exceeding 550, its deficiency in viscosity at a lowtemperature may fail to contribute effectively to improving the lowtemperature properties of the rubber composition. If the plasticizer hasa proportion of less than 15 parts by weight, its addition may not proveto be satisfactory, and if its proportion exceeds 30 parts by weight, itis feared that it may adversely affect the fuel impermeability of therubber composition and may bleed from the base material. The rubbercomposition according to the first aspect of this invention isunsuitable as a material for an outer wall layer of a fuel hose having amultilayer wall structure, or for a fuel hose having a single-layerwall, since it does not have any PVC blended with NBR.

According to a second aspect of this invention, there is provided arubber composition for a fuel transporting hose for a vehicle whichcomprises a blended base material obtained by blending NBR having an ANcontent of 46 to 52 percent by weight and PVC in an amount of less than25 percent by weight relative to NBR, and 15 to 30 parts by weight of aplasticizer having an SP value of 8.8 or more and a molecular weight of550 or less, relative to 100 parts by weight of the base material.

According to the second aspect of this invention which employs a blendedbase material obtained by blending NBR having an AN content of 46 to 52percent by weight and less than 25 percent by weight of PVC, the actionof NBR having an ultrahigh AN content and a certain contribution of PVCto fuel impermeability make it possible to achieve a high level of fuelimpermeability which is comparable to that of FKM. The composition alsocontains the same amount of the same plasticizer as in the first aspectof this invention. Therefore, it is possible to obtain variousoperations and efffects from the addition of a proper amount of aplasticizer having a proper SP value and molecular weight, as is thecase with the first aspect of this invention. The effects by the properaddition of carbon black (CB) can also be obtained. The rubbercomposition according to the second aspect of this invention isunsuitable as a material for an outer wall layer of a fuel hose having amultilayer wall structure, or for a fuel hose having a single-layerwall, since it has a PVC proportion of only less than 25 percent byweight relative to NBR. As its proportion is less than 25 percent byweight, PVC does not appreciably affect a good balance between the fuelimpermeability of the rubber composition and its low temperatureproperties.

According to a third aspect of this invention, the rubber compositionaccording to the first or second aspect thereof satisfies one or more ofthe following (1) to (4):

(1) NBR has an AN content of 48 to 52 percent by weight;

(2) the plasticizer has an SP value of 9.0 or more;

(3) the plasticizer has a molecular weight of 450 or less; and

(4) the plasticizer has a proportion of 20 to 25 parts by weightrelative to 100 parts by weight of the base material.

The rubber composition satisfying one or more of the foregoing (1) to(4) is a particularly good rubber composition.

According to a fourth aspect of this invention, the rubber compositionaccording to any of the first to third aspects thereof satisfies thefollowing (5) and/or (6):

(5) it has a volume specific resistance not exceeding 10⁸Ω·cm; and

(6) it has a hardness of 55 to 75 degrees as measured by a JIS K6253(ISO 48) durometer, type A.

The good conductivity of the rubber composition containing a properamount of a proper type of CB and thereby satisfying the foregoing (5)makes it possible to prevent effectively any inconvenience caused by anelectrostatic charge, including sparking during fill-up, as mentionedbefore. The rubber composition having a hardness satisfying theforegoing (6) as measured by a JIS K6253 (ISO 48) durometer, type A,owing to the proper addition of plasticizer and CB can make a fuel hosefor a vehicle having a practically suitable level of hardness orsoftness.

According to a fifth aspect of this invention, there is provided a fueltransporting hose for a vehicle having an inner wall layer formed from arubber composition according to any of the first to fourth aspects ofthis invention and an outer wall layer formed from a rubber material ofhigh weatherability and ozone resistance, and further including areinforcing yarn layer formed between the inner and outer wall layers,if required.

The rubber composition according to any of the first to fourth aspectsof this invention is low in weatherability and ozone resistance, sinceits base material is NBR not blended with PVC, or NBR blended with onlyless than 25 percent by weight of PVC, though it has a good balancebetween fuel impermeability and low temperature properties and goodconductivity. The construction of the fuel transporting hose for avehicle according to the fifth aspect of this invention ensures its highweatherability and ozone resistance, while it retains the advantages ofthe rubber composition, such as its fuel impermeability and goodconductivity. The reinforcing yarn layer between the inner and outerwall layers ensures an improved hose strength as an additionaladvantage.

According to a sixth aspect of this invention, there is provided a fueltransporting hose for a vehicle having an inner wall layer formed from arubber composition as set forth at (7) below and an outer wall layerformed from a rubber composition as set forth at (8) below, and furtherincluding a reinforcing yarn layer formed between the inner and outerwall layers, if required:

(7) a rubber composition comprising: as a base material NBR having an ANcontent of 48 to 52 percent by weight, or such NBR blended with lessthan 5 percent by weight of PVC; and 15 to 25 parts by weight of aplasticizer having an SP value of 8.8 or more and a molecular weight of550 or less, relative to 100 parts by weight of the base material; and

(8) a rubber composition comprising: as a base material a blend of NBRhaving an AN content of 43 to 50 percent by weight and 25 to 40 percentby weight of PVC; and 15 to 35 parts by weight of a plasticizer havingan SP value of 8.8 or more and a molecular weight of 550 or less,relative to 100 parts by weight of the base material.

The rubber composition (7) for the inner wall layer of the hoseaccording to the sixth aspect of this invention contains as its basematerial NBR having an AN content shifted to the ultrahigh side ascompared with the rubber composition according to the first aspect ofthis invention, or NBR-PVC containing a very small amount of PVC ascompared with the rubber composition according to the second aspect ofthis invention, and further contains a similar amount of a similarplasticizer. Therefore, the rubber composition has a particularly goodbalance between its fuel impermeability and low temperature properties,and as there is no substantial meaning in blending PVC with NBR havingan ultrahigh AN content of 48 to 52 percent by weight, the rubbercomposition hardly has its fuel impermeability affected, even if theamount of PVC is less than 5 percent by weight, or even zero. The rubbercomposition (8) for the outer wall layer is of satisfactorily highweatherability and ozone resistance, while having certain levels of fuelimpermeability and low temperature properties at the same time, asstated at (1) before. Thus, the hose according to the sixth aspect ofthis invention is comparable or even superior in fuel impermeability tothat according to the fifth aspect thereof, can realize goodconductivity, and can also realize low temperature properties asrequired. The reinforcing yarn layer further formed between the innerand outer wall layers brings about an improved hose strength as anadditional advantage to the fuel transporting hose according to thesixth aspect of the invention.

According to a seventh aspect of the invention, there is provided a fueltransporting hose for a vehicle in which the rubber composition (7)according to the sixth aspect of this invention satisfies one or more ofthe following (9) to (12) and/or the rubber composition (8) according tothe sixth aspect of this invention satisfies one or both of thefollowing (10) and (11):

(9) NBR has an AN content of 50 to 52 percent by weight;

(10) the plasticizer has an SP value of 9.0 or more;

(11) the plasticizer has a molecular weight of 450 or less; and

(12) the plasticizer is added in an amount of 18 to 23 parts by weightrelative to 100 parts by weight of the base material.

According to the seventh aspect of this invention, it is possible torealize a particularly good rubber composition if the rubber composition(7) according to the sixth aspect of this invention satisfies one ormore of (9) to (12).

According to an eighth aspect of this invention, there is provided afuel transporting hose for a vehicle in which the rubber composition (7)and/or (8) according to the sixth or seventh aspect of this inventionsatisfies the following (13) and/or (14):

(13) the rubber composition has a volume specific resistance notexceeding 10⁸Ω·cm; and

(14) it has a hardness of 55 to 75 degrees as measured by a JIS K6253(ISO 48) durometer, type A.

According to the eighth aspect of this invention, the good conductivityof the rubber composition (7) and/or (8) containing a proper amount of aproper type of CB and thereby having its volume specific resistanceadjusted as stated at (13) makes it possible to prevent effectively anyinconvenience caused by an electrostatic charge, including sparkingduring fill-up, as mentioned before. The rubber composition having itshardness adjusted as stated at (14) owing to the proper addition ofplasticizer and CB can make a fuel hose for a vehicle having apractically suitable level of hardness or softness.

According to a ninth aspect of this invention, there is provided a fueltransporting hose for a vehicle having an inner wall layer formed fromthe rubber composition (7) according to any of the sixth to eighthaspects of this invention and an outer wall layer formed from a rubbermaterial of high weatherability, ozone resistance and cure flatting(flatting during curing) resistance, and further including a reinforcingyarn layer formed between the inner and outer wall layers, if required.

The rubber composition (7) according to any of the sixth to eighthaspects of this invention tends to lack flatting resistance during cureunder heat, since its base material is NBR having an ultrahigh ANcontent, or NBR blended with only less than 25 percent by weight of PVC,though it has a good balance between fuel impermeability and lowtemperature properties and good conductivity. The construction of thehose according to the ninth aspect of this invention ensures its highweatherability, ozone resistance and cure flatting resistance, while itretains the advantages of the rubber composition, such as its fuelimpermeability, low temperature properties and conductivity. As one ofits specific advantages, its pan cure with no mandrel can be carried outwithout any problem, even if the hose may be of a relatively largediameter like a breather hose. The reinforcing yarn layer further formedbetween the inner and outer wall layers ensures an improved hosestrength as an additional advantage to the fuel transporting hoseaccording to the ninth aspect of the invention.

MODES OF CARRYING OUT THE INVENTION

Rubber Compositions:

The rubber compositions according to this invention are roughlyclassified into the rubber composition according to the first aspect,the rubber composition according to the second aspect, the rubbercomposition (7) according to the sixth aspect and the rubber composition(8) according to the sixth aspect. Modes of putting these rubbercompositions into practice will now be described below.

1. Rubber Composition According to the First Aspect:

The rubber composition according to the first aspect of this inventionis a rubber composition used for a fuel transporting hose for a vehicle,comprising NBR having an AN content of 46 to 52 percent by weight as abase material and 15 to 30 parts by weight of a plasticizer having an SPvalue of 8.8 or more and a molecular weight of 550 or less, relative to100 parts by weight of the base material. Because of its lowweatherability and ozone resistance as stated before, it is unsuitableas a material for an outer wall layer of a fuel hose having a multilayerwall structure, or as a material for a fuel hose having a single-layerwall, and is suitable for use as a material for an inner wall layer of afuel hose having a multilayer wall structure.

The rubber composition has a particularly good fuel impermeability ifits NBR has an AN content of 48 to 52 percent. A plasticizer having anSP value of 9.0 or more is particularly well miscible with NBR to effecta great improvement in the low temperature properties of the rubbercomposition and is particularly unlikely to lower its fuelimpermeability. A plasticizer having a molecular weight of 450 or lessis remarkably low in viscosity at a low temperature and remarkablyimproves the low temperature properties of the rubber composition. Theaddition of the plasticizer produces the best-balanced result if itsamount is 20 to 25 parts by weight relative to 100 parts by weight ofNBR.

An ether-ester type plasticizer, such as ADEKA CIZER RS-107 or RS-540(tradename) of Asahi Denka Kogyo K.K., can be mentioned as a preferredplasticizer, though any other type of plasticizer can also be used if itsatisfies the conditions as stated above.

The rubber composition preferably has a volume specific resistance notexceeding 10⁸Ω·cm by the proper addition of CB and/or a hardness of 55to 75 degrees (as measured by a JIS K6253 (ISO 48) durometer, type A) bythe well-balanced addition of plasticizer and CB. The amount of CB to beadded may, for example, be about 20 to 100 parts by weight relative to100 parts by weight of NBR, though it cannot be expressed by a definitevalue, since it varies with the amount of the plasticizer, the kind ofCB, etc. While any kind of CB can be used, it is preferable to use CBhaving a relatively small particle diameter and a large structure andcontributing greatly to conductivity and it is possible to use with orinstead of such CB conductive carbon, such as acetylene black or KetchenBlack. It is also possible to use any conductivity agent other than CBif it does not affect impermeability adversely.

The rubber composition according to the first aspect of this inventionmay further contain various kinds of other known additives, such as avulcanizing agent, a vulcanization accelerator, a white reinforcingagent and an antioxidant agent. As a vulcanizing agent, it is preferableto use one which is commonly used for NBR, particularly a low-sulfurone. As regards a white reinforcing agent, such as silica or calciumcarbonate, it is generally preferable not to add anything, except to anyrubber composition having a special purpose, such as the rubbercomposition (8) according to the sixth aspect of this invention, in viewof any undesirable effect that it may have on the fuel impermeability,low temperature properties, conductivity, etc. of the rubbercomposition, and if anything is added, it is preferable to add only upto 10 parts by weight relative to 100 parts by weight of NBR or NBR-PVC.

2. Rubber Composition According to the Second Aspect:

The rubber composition according to the second aspect of this inventionis a rubber composition used for a fuel transporting hose for a vehicle,comprising NBR having an AN content of 46 to 52 percent by weight andblended with less than 25 percent by weight of PVC as a base materialand 15 to 30 parts by weight of a plasticizer having an SP value of 8.8or more and a molecular weight of 550 or less, relative to 100 parts byweight of the base material. Because of its low weatherability and ozoneresistance, though it is better than the rubber composition according tothe first aspect, it is unsuitable as a material for an outer wall layerof a fuel hose having a multilayer wall structure, or as a material fora fuel hose having a single-layer wall, and is suitable for use as amaterial for an inner wall layer of a fuel hose having a multilayer wallstructure.

It is preferable for the rubber composition that NBR have an AN contentof 48 to 52 percent, and that the plasticizer have an SP value of 9.0 ormore, a molecular weight of 450 or less and a proportion of 20 to 25parts by weight relative to 100 parts by weight of NBR, as has been thecase with the rubber composition according to the first aspect of thisinvention, while the use of the same kind of plasticizer is alsopreferred.

It is preferable for the rubber composition to have a volume specificresistance not exceeding 10⁸Ω·cm by the addition of CB and a hardness of55 to 75 degrees (as measured by a JIS K6253 (ISO 48) durometer, type A)by the well-balanced addition of plasticizer and CB, as has been thecase with the rubber composition according to the first aspect of thisinvention, while the kind and amount of CB are also preferred. Moreover,the statements made before in connection with the addition of variousknown additives and the kinds and addition of vulcanizing and whitereinforcing agents for the rubber composition according to the firstaspect of this invention are also applicable to the rubber compositionaccording to the second aspect thereof.

3. Rubber Composition (7) According to the Sixth Aspect:

The rubber composition (7) according to the sixth aspect of thisinvention is a rubber composition used for an inner wall layer of a fueltransporting hose for a vehicle, comprising NBR having an AN content of48 to 52 percent by weight or such NBR blended with less than 5 percentby weight of PVC as a base material, and 15 to 25 parts by weight of aplasticizer having an SP value of 8.8 or more and a molecular weight of550 or less, relative to 100 parts by weight of the base material.

The rubber composition differs from the rubber composition according tothe first or second aspect of this invention in that NBR has an ANcontent shifted to a still ultrahigh range of 48 to 52 percent byweight, and that if any PVC is blended, it has a proportion of less than5 percent by weight, and though it may be improved in fuelimpermeability, while remaining relatively the same in low temperatureproperties, it is inferior to the rubber composition according to thesecond aspect of this invention in weatherability and ozone resistance,and is also suitable for use as a material for an inner wall layer of afuel hose having a multilayer wall structure.

The rubber composition is remarkably improved in fuel impermeability ifits NBR has an AN content of 50 to 52 percent and/or the plasticizer hasa proportion of 18 to 23 parts by weight relative to 100 parts by weightof the base material, and for the same reason as stated for the rubbercomposition according to the first aspect of this invention, it ispreferable that the plasticizer has an SP value of 9.0 or more and amolecular weight of 450 or less. The plasticizer preferred for therubber composition according to the first aspect is also preferred.

It is preferable for the rubber composition to have a volume specificresistance not exceeding 10⁸Ω·cm by the addition of CB and a hardness of55 to 75 degrees (as measured by a JIS K6253 (ISO 48) durometer, type A)by the well-balanced addition of plasticizer and CB, as has been thecase with the rubber composition according to the first aspect of thisinvention. Moreover, also applicable are the statements made before inconnection with the preferred kind and amount of CB, the addition ofvarious known additives and the kinds and addition of vulcanizing andwhite reinforcing agents for the rubber composition according to thefirst aspect of this invention.

4. Rubber Composition (8) According to the Sixth Aspect:

The rubber composition (8) according to the sixth aspect of thisinvention is a rubber composition used for an outer wall layer of a fueltransporting hose for a vehicle, comprising a blended base materialobtained by blending 25 to 40 percent by weight of PVC with NBR havingan AN content of 43 to 50 percent by weight, and 15 to 35 parts byweight of a plasticizer having an SP value of 8.8 or more and amolecular weight of 550 or less, relative to 100 parts by weight of thebase material.

The rubber composition differs from the rubber composition according tothe first or second aspect of this invention in that NBR has an ANcontent shifted to a somewhat lower range of 43 to 50 percent by weight,while PVC has a higher proportion of 25 to 40 percent by weight, andthat the plasticizer also has a somewhat higher proportion, and thoughit may be relatively difficult to maintain a good balance between itsfuel impermeability and low temperature properties, it is of good fuelimpermeability owing to the high proportion of PVC and of highweatherability and ozone resistance owing to PVC. Therefore, it issuitable as a material for an outer wall layer of a fuel hose having amultilayer wall structure, or for a fuel hose having a single walllayer.

For the same reason as stated for the rubber composition according tothe first aspect of this invention, it is preferable that theplasticizer has an SP value of 9.0 or more and a molecular weight of 450or less. The plasticizer preferred for the rubber composition accordingto the first aspect is also preferred.

It is preferable for the rubber composition to have a hardness of 55 to75 degrees (as measured by a JIS K6253 (ISO 48) durometer, type A) ashas been the case with the rubber composition according to the firstaspect of this invention. Almost equally applicable are the statementsmade before in connection with the preferred kind and amount of CB, theaddition of various known additives and the kinds and addition ofvulcanizing and white reinforcing agents for the rubber compositionaccording to the first aspect of this invention.

Rubber Material for the Outer Wall Layer of the Hose According to theFifth or Ninth Aspect of the Invention:

The rubber material forming the outer wall layer of the hose accordingto the fifth aspect of this invention is a certain rubber material ofhigh weatherability or ozone resistance, and specific examples includeECO (epichlorohydrin rubber), CSM (chlorosulfonated polyethylenerubber), NBR-PVC, NE (NBR-EPDM, or a blend of NBR and anethylene-propylene-diene terpolymer), etc. It may also be a blendcomposed mainly of any of those materials, or may contain various kindsof additives, if it is certainly of high weatherability or ozoneresistance.

The rubber material forming the outer wall layer of the hose accordingto the ninth aspect of this invention is a certain rubber material ofhigh ozone resistance and cure flatting resistance, and is a material(or mixture) having a sufficiently high viscosity to support its ownweight at a high temperature for cure and a sufficiently highvulcanizing speed to overcome any flatting under: heat during cure toremain in shape, a specific example being possibly a mixture containinga large amount of a thickening agent, such as silica.

Fuel Transporting Hoses for Vehicles:

The fuel transporting hose for a vehicle according to the fifth aspectof this invention is a hose having an inner wall layer formed from therubber composition according to any of the first to fourth aspectsthereof and an outer wall layer formed from a certain rubber material ofhigh weatherability or ozone resistance as stated before; the fueltransporting hose according to the sixth aspect of this invention is ahose having an inner wall layer formed from the rubber composition (7)and an outer wall layer formed from the rubber composition (8) asdescribed before; and the fuel transporting hose according to the ninthaspect of this invention is a hose having an inner wall layer formedfrom the rubber composition (7) and an outer wall layer formed from acertain rubber material of high ozone resistance and cure flattingresistance as stated before. The thicknesses of the inner and outer walllayers of each such hose may be selected appropriately in accordancewith the total wall thickness of the hose, the fuel impermeability asrequired and other properties of the hose, but the inner wall layerpreferably has a thickness equal to at least a half of the total wallthickness of the hose.

Each fuel transporting hose may contain any element for forming a hose,such as an intermediate reinforcing yarn layer, if required in additionto the inner and outer wall layers. However, the hose preferably has itsinnermost wall layer formed by the inner wall layer as described above.In the event that a reinforcing yarn layer is formed, there is nolimitation as to the kind of reinforcing yarn or the formation of thelayer (braiding, spiral winding in one or more layers, the presence ofan intermediate rubber layer, etc.). All of the hoses can be usedwithout limitation for various purposes as fuel transporting hoses forvehicles, and are particularly suitable for use as filler neck hoses, orbreather or evaporation hoses in vapor lines, and the hose according tothe ninth aspect of this invention is, among others, suitable as a hosehaving a relatively large diameter, e.g. a breather hose, in the eventthat efficient pan cure with no mandrel is desired.

Process for Manufacturing a Fuel Transporting Hose for a Vehicle:

The fuel transporting hoses for vehicles as described can bemanufactured by any known method. The hose according to the ninth aspectof this invention can be made with a considerably large diameter byextrusion, and pan cured directly. The other hoses are, however, likelyto be flatted easily in their molded form yet to be cured, and thefollowing manufacturing processes can, for example, be relied upon assuitable countermeasures.

Firstly, an uncured molded product for a straight or curved hose havinga single-layer or multilayer wall structure is extruded in a straightform, and cured by heating, while its straight or curved tubular shapeis maintained by a straight or curved mandrel inserted through it, or bya heating die having the molded product fitted in its straight or curvedgroove. This process is suitable for making, among others, a breatherhose.

Secondly, a straight, curved or at least partly corrugated tubularcavity is formed in a mold containing a mandrel and capable of beingheated and an uncured rubber material is introduced into the cavity andcured by the heat of the heated mold to make a straight, curved or atleast partly corrugated hose. The hose removed from the mold aftercuring may be further heated by any appropriate method for acceleratedcuring. This process is suitable for making, among others, a fillerhose.

BEST MODE OF CARRYING OUT THE INVENTION:

Formulations for Uncured Rubber Compositions:

Referring first to Comparative Example 1, there was employed afluororubber (FKM) composition prepared by mixing 100 parts by weight ofFluorel FE5731Q (tradename) of Sumitomo 3M, which was FKM having afluorine content of 69 percent and containing an internal polyolvulcanizing agent, 3 parts by weight of MgO, 6 parts by weight ofCa(OH)₂ and 15 parts by weight of CB.

Then, formulations were established to prepare test specimens of rubbercompositions according to Examples 1 to 10 as shown in Tables 1 and 2,Comparative examples 2 to 11 as shown in Tables 3 and 4, and Examples2-1 and 2-2 and Comparative examples 2-1 and 2-2 as shown in Table 5 inaccordance with the basic formulation as shown below and by adding awhite reinforcing agent in certain cases as shown in the relevanttables.

TABLE 1 1 2 3 4 5 6 7 8 AN content 50 52 46 46 46 50 50 50 Amount of PVC0 0 0 15 25 0 0 0 Molecular weight of plasticizer 434 434 434 434 434550 434 434 SP value of plasticizer 9.2 9.2 9.2 9.2 9.2 8.9 9.2 9.2Amount of plasticizer (phr) 23 23 23 23 23 23 15 30 Carbon grade FEF FEFFEF FEF FEF FEF HAF FEF Amount of carbon (phr) 40 40 40 40 40 40 30 50Conductive carbon — — — — — — — — Amount of conductive carbon (phr) — —— — — — — — White reinforcing agent — — — — — — — — Amount of whitereinforcing agent — — — — — — — — Physical properties in ordinary stateTensile strength (MPa) 15.5 11.7 14.7 16.6 16.3 15.0 17.8 13.9Elongation (%) 570 390 650 560 510 590 520 490 Hardness (HA) 62 65 60 6670 60 68 61 Gasoline permeability (PHASE II) 0.7 0.4 6.0 3.8 3.0 1.1 0.53.8 Permeation coefficient (mg · mm/cm²/day) Brittle temperature (° C.)−28 −25 −34 −28 −23 −23 −21 −32 Volume specific resistance (Ω · cm) 2 ×10⁷ 7 × 10⁷ 3 × 10⁷ 6 × 10⁷ 5 × 10⁷ 1 × 10⁷ 1 × 10⁸ 3 × 10⁶ Bleeding NoNo No No No No No No Workability Good Good Good Good Good Good Good Good

TABLE 2 9 10 AN content 50 50 Amount of PVC 0 0 Molecular weight ofplasticizer 434 434 SP value of plasticizer 9.2 9.2 Amount ofplasticizer (phr) 23 23 Carbon grade HAF HAF Amount of carbon (phr) 2520 Conductive carbon Ketchen Ketchen Amount of conductive carbon (phr) 55 White reinforcing agent — Talc Amount of white reinforcing agent — 10Physical properties in ordinary state Tensile strength (MPa) 15.0 12.3Elongation (%) 380 430 Hardness (HA) 69 68 Gasoline permeability (PHASEII) 1.5 1.0 Permeation coefficient (mg · mm/cm²/day) Brittle temperature(° C.) −23 −21 Volume specific resistance (Ω · cm) 1 × 10⁶ 5 × 10⁷Bleeding No No Workability Good Good

TABLE 3 1 2 3 4 5 6 7 AN content Ternary FKM 43.5  50  50  50  50  50Amount of PVC containing 69%  0  0  0  0  0  0 F Molecular weight ofplasticizer — 434 434 434 371 850 434 SP value of plasticizer —  9.2 9.2 9.2 8.5 9.2  9.2 Amount of plasticizer (phr) —  23  10  35  23  23 23 Carbon grade SRF FEF HAF FEF FEF FEF HAF Amount of carbon (phr)  15 40  25  60  40  40  20 Conductive carbon — — — — — — — Amount ofconductive carbon (phr) — — — — — — — White reinforcing agent — — — — —— Silica Amount of white reinforcing agent — — — — — —  20 Physicalproperties in ordinary state Tensile strength (MPa) 12.5 14.6 17.9 14.0*15.6* 15.2* 13.2 Elongation (%) 350 630 620 560 450 520 480 Hardness(HA)  70  60  60  63  66  65  67 Gasoline permeability (PHASE II)  0.711.4  0.4 9.5*  0.9*  2.6*  8.9 Permeation coefficient (mg · mm/cm²/day)Brittle temperature (° C.) −20 −34 −17 −34* −15* −18* −19 Volumespecific resistance (Ω · cm) 1 × 10¹¹ 1 × 10⁸ 7 × 10⁸ 1 × 10^(6*) 8 ×10^(6*) 2 × 10^(7*) 8 × 10⁹ Bleeding No No No Yes Yes Yes No WorkabilityGood Good Good Bad Bad Good* Good *Only for reference due to plasticizerbleeding

TABLE 4 8 9 10 11 AN content 50 50 50 50 Amount of PVC 0 0 0 0 Molecularweight of 434 434 434 434 plasticizer SP value of plasticizer 9.2 9.29.2 9.2 Amount of plasticizer (phr) 23 23 23 23 Carbon grade HAF HAF HAFFT Amount of carbon (phr) 20 20 20 80 Conductive carbon — — — — Amountof conductive — — — — carbon (phr) White reinforcing agent Calcium MicaTalc — carbonate Amount of white 30 30 30 — reinforcing agent Physicalproperties in ordinary state Tensile strength (MPa) 12.3 10.8 12.5 10.5Elongation (%) 480 380 390 360 Hardness (HA) 59 57 62 59 Gasolinepermeability 15.3 0.6 0.5 0.5 (PHASE II) Permeation coefficient (mg ·mm/cm²/day) Brittle temperature (° C.) −14 −14 −17 −24 Volume specificresistance 3 × 10¹⁰ 1 × 10¹⁰ 2 × 10¹⁰ 4 × 10⁹ (Ω · cm) Bleeding No No NoNo Workability Good Bad Good Good

TABLE 5 Comparative Comparative Example Example Example Example 2-1 2-22-1 2-2 Polymer NBR-PVC NBR-PVC NBR-PVC NBR-PVC AN content 46 40 46 35Amount of PVC 30 30 30 30 Molecular weight 434 391 434 391 ofplasticizer SP value of 9.2 9.0 9.2 9.0 plasticizer Amount of 25 25 3530 plasticizer (phr) Carbon grade FEF SRF FEF FEF Amount of carbon 10 1055 65 (phr) White reinforcing Silica Silica — — agent Amount of white 4040 — — reinforcing agent Physical properties in ordinary state Tensilestrength 14.8 17.7 14.2 14.5 (MPa) Elongation (%) 450 500 550 510Hardness (HA) 73 70 69 68 Gasoline 18.7 50.5 9.1 80.5 permeability(PHASE II) Permeation coefficient (mg · mm/cm²/day) Cure flatting GoodGood Bad Bad resistance Bleeding No No No No Workability Good Good GoodGood

Tables 1 to 4 show the formulations for Examples and ComparativeExamples each intended for a material for the inner wall layer of a fuelhose for a vehicle and Table 5 shows the formulations for Examples andComparative Examples each intended for the rubber composition (8)according to the sixth aspect of this invention or the rubber materialfor the outer wall layer according to the ninth aspect of thisinvention.

Basic Formulation

Polymer—100 parts by weight

Zinc oxide—5 parts by weight

Stearic acid—1 part by weight

Antioxidant—2 parts by weight

Carbon black (CB)—Variable

Plasticizer—Variable

Sulfur—0.5 part by weight

Thiuram vulcanization accelerator—1.5 parts by weight

Sulfenamide vulcanization accelerator—1.5 parts by weight

The polymer in the basic formulation is NBR or NBR-PVC having adifferent PVC proportion and a different AN content in NBR as shown ineach table. In the tables, the AN content and the PVC proportion areboth shown by weight percentage.

ADEKA CIZER RS107 (tradename) of Asahi Denka Kogyo K.K. was employed asthe plasticizer in each of Examples 1 to 5 and 7 to 10, ComparativeExamples 2 to 4 and 7 to 11, Example 2-1 and Comparative Example 2-1,ADEKA CIZER RS700 (tradename) of Asahi Denka Kogyo K.K. in Example 6,DOA in Comparative Example 5, ADEKA CIZER RS735 (tradename) of AsahiDenka Kogyo K.K. in Comparative Example 6, and DOP in Example 2—2 andComparative Example 2—2, all used in the amount shown by phr (parts perhundred parts of rubber: parts by weight relative to 100 parts by weightof polymer). The SP value and molecular weight of the plasticizer arealso shown in each table.

Each table shows the carbon black employed as Carbon grade, i.e. ShowBlack N330 (tradename) of Showa Cabot K.K. as HAF, Seast SO (tradename)of Tokai Carbon Co., Ltd. as FEF, Seast S (tradename) of Tokai CarbonCo., Ltd. as SRF and Asahi Thermal (tradename) of Asahi Carbon Co., Ltd.as FT, together with its amount shown by phr.

In some Examples or Comparative Examples, Ketchen Black (Ketchen BlackEC (tradename) of Ketchen International Co.) was used as conductivecarbon instead of CB or in addition to it as shown by phr in the tables.

In certain Examples and Comparative Examples, a white reinforcing agentof the type shown in each relevant table was used in the amount shown byphr. The tables show NIPSIL ER (tradename) of Nippon Silica K.K. asSilica, Hakuenka CC (tradename) of Shiraishi Calcium Kaisha, Ltd. asCalci-um carbonate, Canna Mica M-200 (tradename) of KMG Minerals, Inc.as Mica and Mistron Vapor (tradename) of Sierra Talc Co. as Talc.

Ozonon 3C (tradename) or NONFLEX RD (tradename) of Seiko Chemical Co.,Ltd. was used as the antioxidant, Nocceler TT-G or Nocceler CZ-G(tradename) of Ouchi Shinko Chemical Industrial Co., Ltd. as thevulcanization accelerator, and sulfur PTC as the vulcanizing agent.

Preparation of Test Specimens:

The uncured rubber composition according to each example was prepared bymixing in a Banbury mixer and open rolls in accordance with the relevantformulation, and press cured at 150° C. for 30 minutes (160° C. for 45minutes in Comparative Example 1) to form a sheet having a thickness of2 mm to prepare a test specimen in sheet form.

Evaluation for Physical Properties in Ordinary State:

The test specimens according to each example were tested for tensilestrength (MPa), elongation (%) and hardness (HA as measured by a type Adurometer) as physical properties in an ordinary state in accordancewith JIS K6251. (ISO 37) and JIS K6253 (ISO 48). The results are shownin Tables 1 to 5. A tensile strength of 10.0 MPa or more, an elongationof 300% or more and a hardness (HA) of 55 to 75 degrees are consideredas the preferred physical properties.

Evaluation for Gasoline Permeability:

The evaluation of the test specimen according to each example for itsgasoline permeability was made by measuring its permeation coefficient(mg·mm/cm²/day) in accordance with the CUP method using PHASE IIgasoline as stated before. The CUP method is carried out by placinggasoline in a specific cup-shaped device, closing the opening of the cup(having an open area of P cm²) tightly with the test specimen in theform of a sheet having a thickness of t (mm) and turning the wholedevice upside down to dip one side of the specimen in the gasoline.

More particularly, pretreatment is carried out by placing 100 ml ofgasoline in the cup, leaving one side of the specimen dipped in thegasoline at 40° C. for seven days, changing the gasoline to 100 ml ofnew gasoline and measuring the total weight W0 (mg) including the cup.Then, the specimen has one side thereof left dipped in the gasoline at40° C. for three days, the total weight W1 (mg) including the cup ismeasured immediately thereafter, and the permeation coefficient iscalculated in accordance with an equation: Permeationcoefficient=t(W0−W1)/3P.

The permeation coefficient as calculated is shown in each relevanttable. A permeation coefficient of 10.0 or less is preferred, and astill higher level of impermeability (e.g. a coefficient of 3.0 or less)is considered preferable for the rubber composition (7) according to thesixth or seventh aspect of this invention of which a higher level ofimpermeability is required.

Evaluation for Low Temperature Properties:

The brittle temperature (° C.) of the test specimen according to each ofthe examples shown in Tables 1 to 4 was measured by a low temperatureimpact test as specified by JIS K6261 (ISO 812). The results are shownin Tables 1 to 4. A brittle temperature of −20° C. or below isconsidered preferable.

Evaluation for Volume Specific Resistance:

The volume specific resistance (ohms cm) of the test specimen accordingto each of the examples shown in Tables 1 to 4 was determined by a testusing a voltage of 1 to 100 V in accordance with JIS K6911 (IEC 93). Theresults are shown in Tables 1 to 4. A volume specific resistance notexceeding 10⁸Ω·cm is considered preferable.

Evaluation for Cure Flatting Resistance:

A truly circular hose having a single-layer wall with an inside diameterof 13 mm and an outside diameter of 21 mm was extruded from the uncuredrubber composition according to each of the examples shown in Table 5,and after 30 minutes of curing at 150° C. in a steam cure oven, itscross-sectional height was compared with what it had been before itscuring. A difference of 5% or less is desirable, and the compositionwhich conformed to that standard is shown as Good in the table, and thatwhich did not is shown as Bad.

Evaluation for Other Items:

The test specimen according to each of the examples shown in Tables 1 to4 was examined for any bleeding on the sheet surface after it had beenleft to stand at normal temperature for a week after curing. If nobleeding was found, it is shown as No in the relevant table, and if anybleeding was found, it is shown as Yes.

An overall evaluation of the test specimen according to each of theexamples shown in Tables 1 to 5 for workability by examining its Banburyand roll workability, and extrusion processability. The workability ofeach composition is shown as Good if there was no problem, and as Bad ifthere was any problem.

INDUSTRIAL UTILITY

As is obvious from the foregoing, the rubber composition of thisinvention is a simple mixture of inexpensive constituents which canrealize a high level of fuel impermeability, while ensuring otherproperties, such as low temperature properties. The conductivity asrequired of certain fuel transporting hoses for vehicles is also easy tosatisfy. The fuel transporting hose of this invention formed from anysuch rubber composition is easy to manufacture at a low cost and yet canrealize a high level of fuel impermeability, and good conductivity ifdesired.

What is claimed is:
 1. A rubber composition useful for a fueltransporting hose for a vehicle, comprising a) NBR having an AN contentof from 46 to 52 percent by weight as a base material and b) from 15 to30 parts by weight of a plasticizer having an SP value of 8.8 or moreand a molecular weight of 550 or less, relative to 100 parts by weightof the base material.
 2. The rubber composition according to claim 1,which satisfies at least one of the following (1) to (4): (1) the NBRhas an AN content of 48 to 52 percent by weight; (2) the plasticizer hasan SP value of 9.0 or more; (3) the plasticizer has a molecular weightof 450 or less; and (4) the plasticizer has a proportion of from 20 to25 parts by weight relative to 100 parts by weight of the base material.3. The rubber composition according to claim 1, which satisfies thefollowing (5) and/or (6): (5) it has a volume specific resistance notexceeding 10⁸Ω·cm; and (6) it has a hardness of from 55 to 75 degrees asmeasured by a JIS K6253 (ISO 48) durometer, type A.
 4. A rubbercomposition for a fuel transporting hose for a vehicle, comprising: a) ablended base material which is a blend of NBR having an AN content offrom 46 to 52 percent by weight and less than 25 percent by weight ofPVC, and b) from 15 to 30 parts by weight of a plasticizer having an SPvalue of 8.8 or more and a molecular weight of 550 or less, relative to100 parts by weight of the base material.
 5. The rubber compositionaccording to claim 4, which satisfies at least one of the following (1)to (4): (1) the NBR has an AN content of 48 to 52 percent by weight; (2)the plasticizer has an SP value of 9.0 or more; (3) the plasticizer hasa molecular weight of 450 or less; and (4) the plasticizer has aproportion of from 20 to 25 parts by weight relative to 100 parts byweight of the base material.
 6. The rubber composition according toclaim 4, which satisfies the following (5) and/or (6): (5) it has avolume specific resistance not exceeding 10⁸Ω·cm; and (6) it has ahardness of from 55 to 75 degrees as measured by a JIS K6253 (ISO 48)durometer, type A.
 7. A fuel transporting hose for a vehicle comprisingan inner wall layer of the rubber composition according to claim 1 andan outer wall layer of a rubber material of high weatherability andozone resistance.
 8. The hose according to claim 7, further comprising areinforcing yarn layer formed between the inner and outer wall layers.9. A fuel transporting hose for a vehicle comprising an inner wall layerof a rubber composition (7) and an outer wall layer of a rubbercomposition (8): (7) a rubber composition comprising NBR having an ANcontent of from 48 to 52 percent by weight, or a blend of such NBR andless than 5 percent by weight of PVC as a base material and from 15 to25 parts by weight of a plasticizer having an SP value of 8.8 or moreand a molecular weight of 550 or less, relative to 100 parts by weightof the base material; and (8) a rubber composition comprising a blendedbase material, which is a blend of NBR having an AN content of from 43to 50 percent by weight and from 25 to 40 percent by weight of PVC, andfrom 15 to 35 parts by weight of a plasticizer having an SP value of 8.8or more and a molecular weight of 550 or less, relative to 100 parts byweight of the base material.
 10. The hose according to claim 9, furthercomprising a reinforcing yarn layer formed between the inner and outerwall layers.
 11. The hose according to claim 9, wherein the rubbercomposition (7) satisfies at least one of the following (9) to (12): (9)the NBR has an AN content of from 50 to 52 percent by weight; (10) theplasticizer has an SP value of 9.0 or more; (11) the plasticizer has amolecular weight of 450 or less; and (12) the plasticizer has aproportion of from 18 to 23 parts by weight relative to 100 parts byweight of the base material.
 12. The hose according to claim 9, whereinthe rubber composition (8) satisfies one or both of the following (10)and (11): (10) the plasticizer has an SP value of 9.0 or more; and (11)the plasticizer has a molecular weight of 450 or less.
 13. The hoseaccording to claim 9, wherein the rubber composition (7) and/or (8)satisfies the following (13) and/or (14): (13) it has a volume specificresistance not exceeding 10⁸Ω·cm; and (14) it has a hardness of from 55to 75 degrees as measured by a JIS K6253 (ISO 48) durometer, type A. 14.A fuel transporting hose for a vehicle comprising an inner wall layer ofthe rubber composition (7) according to claim 9 and an outer wall layerof a rubber material of high weatherability, ozone resistance and cureflatting resistance.
 15. The hose according to claim 14, furthercomprising a reinforcing yarn layer between the inner and outer walllayers.